Sharks: Survival of the Fittest

Did you know sharks predate dinosaurs by 200 million years? Learn how these predators have survived for so long!

Published July 26, 2017

A prehistoric marine reptile known as Plesiosaurus dolichodeirus and prehistoric sharks in the Hybodus genus were just two types of marine animals that thrived in the ocean during the Jurassic period.

Plesiosaurus dolichodeirus was one of the largest animals in the ocean, growing up to 11 feet long. Hybodus species resembled modern-day sharks, but had a sharp blade in front of their dorsal fins to fend off predators. Both animals hunted small marine animals and lived in shallow water.

About 250 million years ago, plesiosaurus dolichodeirus and many other animals went extinct—but Hybodus species didn't. So how did these two similar animals meet two different fates?

During the first major extinction event, Hybodus species adapted to survive. Hybodus species and other shark species swam to deeper parts of the ocean and adopted a more flexible diet, and eventually evolved into the modern-day sharks we’re familiar with today. Plesiosaurus dolichodeirus continued to live in shallow waters, but temperatures close to the surface rose rapidly. The warmer climate drove Plesiosaurus dolichodeirus and much of its prey to extinction.